lnvoluntary movements have often been difficult to classify clinically. Clinical and physiological analysis of a continuing series of patients has led to new classifications and pathophysiological insights. Dystonias and Parkinson's disease (PD) have been the focus of our recent work. The laboratory has done extensive studies with reciprocal inhibition studies. The conclusion of these studies is that there is an important deficit in reciprocal inhibition in dystonia and PD. There are a number of phases in the reciprocal inhibition curves and the physiology of each is not clear. During further studies of this project, it became clear that the method can be improved and better standardized. Therefore, a study of different parameters that influence the reciprocal inhibition of the H-reflex in wrist flexors was done. Cutaneous reflexes were measured in patients with PD. The reflex is composed of successive excitatory and inhibitory events. While the latencies of the different reflex components and the amplitudes of the excitatory peaks were not different from normal, the first inhibitory peak, occurring at a mean latency of 51 ms, was less pronounced in patients. The result is compatible with the loss of a spinal inhibitory mechanism elicited by cutaneous afferents and can be a partial explanation for increased tone in PD. We developed a technique to evoke perioral reflexes by stimulating branches of the trigeminal nerve either electrically or indirectly via stimulation of cutaneous receptors by delivering well-defined taps to the skin in the vicinity of the lips, mimicking the clinical test. We have established normative data and studied patients suffering from orofacial dyskinesias and spasmodic dysphonia. In both groups of patients, thresholds for eliciting R2 components of facial reflexes were lower and recruitment curves were steeper as compared to normals. We have studied several patients in a family with hyperekplexia. Our results showed that the movement in these patients is an exaggerated startle reflex.